Power/Watts: Independent of Pedal Speed?
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Good point dave...or...these guys were on triples and since they live and die by data, they deliberately slowed their cadence to throw off the competition.
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I don't want to take too much credit. I have it on high authority graphs shown started life as a Rorschach test and then was decided that scale would be added to abscissa and ordinate to create a quantitative analysis.
#128
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Here's a plot from a different rider on a different hill. The hill was about 15 minutes long, and I snipped away the rest of the ride to focus only on that hill. The top two panels show the relationship between power and cadence, and power and crank torque. The two bottom panels show the relationship between cadence and torque. As it happens I can see his choice of gearing at each second of the climb, and the lowest ring-cog combo he used was a 39/23 although he had a 39/25. I think you can see that the relationship between crank torque and power is much stronger than the relationship between cadence and power -- that means this rider is *mostly* using crank torque to modulate his power.
The bottom right panel shows you how the combinations of cadence and crank torque he used were related to his power.
Last edited by RChung; 10-18-17 at 03:32 PM.
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I wonder if the data you see is not more just because the shift takes some mental energy/guess work and is often too big, where the rider can do a mini stomp on the pedal and get the same result.
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I bought one of these CVT/infinite gear bikes for tooling around on and kid's school commute. The bike was heavy and not fun to ride, but changing gear ratio was a very easy turn of the handle, like a motorcycle accelerator. I noticed (no power meter) that I was turning my wrist for little things where I may have just torqued through it.
I wonder if the data you see is not more just because the shift takes some mental energy/guess work and is often too big, where the rider can do a mini stomp on the pedal and get the same result.
I wonder if the data you see is not more just because the shift takes some mental energy/guess work and is often too big, where the rider can do a mini stomp on the pedal and get the same result.
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Then do the opposite: with your existing bike and existing PM,
1) collect data while riding up a hill while shifting normally; then
2) repeat on the same hill while shifting like mad; then
3) repeat on the same hill while keeping the bike in one single gear.
Then see how much the cadence/torque/power relationships vary across your three runs.
1) collect data while riding up a hill while shifting normally; then
2) repeat on the same hill while shifting like mad; then
3) repeat on the same hill while keeping the bike in one single gear.
Then see how much the cadence/torque/power relationships vary across your three runs.
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Power/Watts: Independent of Pedal Speed?
Probably a basic physics question. Is wattage affected by cadence? If, say, two identical riders on identical bikes are riding together, same speed; one is in a large gear pedaling at ~70rpm, while the other is spinning at 110+rpm. Is one producing more watts than the other?
Probably a basic physics question. Is wattage affected by cadence? If, say, two identical riders on identical bikes are riding together, same speed; one is in a large gear pedaling at ~70rpm, while the other is spinning at 110+rpm. Is one producing more watts than the other?
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You, and others apparently, are assuming that this can only mean power at the crank, propelling the bike forward. That assumption is incorrect, and not just technically. He wanted to know if there is any difference in regards to the power a given rider can provide, given different cadences.
Obviously, if you could provide 250 watts for an hour at 80 rpm, and only 200 watts for an hour at 140 rpm, you would have to agree that you produce more watts at the 80 cadence. The situation is nowhere near that drastic, but where there IS even a small difference, it is precisely what he was asking.
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Again, you are reading into the question and adding words the OP did not use. Look at the sentence you quoted. It is "Is one producing more watts than the other?"
Not "Is one [more physiologically efficient such that he is capable of] producing more watts than the other [over a given time]?" Which is an entirely different question you seem to be trying to answer.
I'm not saying you and others are wrong, just that it is literally not the question asked.
Not "Is one [more physiologically efficient such that he is capable of] producing more watts than the other [over a given time]?" Which is an entirely different question you seem to be trying to answer.
I'm not saying you and others are wrong, just that it is literally not the question asked.
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Again, you are reading into the question and adding words the OP did not use. Look at the sentence you quoted. It is "Is one producing more watts than the other?"
Not "Is one [more physiologically efficient such that he is capable of] producing more watts than the other [over a given time]?" Which is an entirely different question you seem to be trying to answer.
I'm not saying you and others are wrong, just that it is literally not the question asked.
Not "Is one [more physiologically efficient such that he is capable of] producing more watts than the other [over a given time]?" Which is an entirely different question you seem to be trying to answer.
I'm not saying you and others are wrong, just that it is literally not the question asked.
If I have expended 800 kilojoules for an hour, and you have expended 1000 for an hour, yet both of our power meters read 250 watts, which of us produced more power?
Secondly, if my drive loses 5% power between the crank and the ground, and your's loses 2%, and both of our crank meters read 250 watts, which of us produced more power?
If he wanted a simple physics answer to torque/cadence/power that's one thing. From the OP post I infer two questions. IS it a basic physics question (no), and what effect does cadence have on power? Do the crank meters read the same - yes, presuming that they're accurate. Include cyclists in the scenario, as he does, well then there's a difference.
#141
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I dont buy the "higher rpm is more efficient" dogma. Try Spinning at 120 rpm on a very light load compared to 80 rpm. At 120 you spend a lot of energy just moving yous legs up and down, spinning the crank, even without doing any real work (moving the bike). Just try it out and you'll see.
#142
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I dont buy the "higher rpm is more efficient" dogma. Try Spinning at 120 rpm on a very light load compared to 80 rpm. At 120 you spend a lot of energy just moving yous legs up and down, spinning the crank, even without doing any real work (moving the bike). Just try it out and you'll see.
(Similarly, the point of high torque is to avoid spinning out. The body has a lot of bottlenecks, and it's all a balancing act.)
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Two things.
If I have expended 800 kilojoules for an hour, and you have expended 1000 for an hour, yet both of our power meters read 250 watts, which of us produced more power?
Secondly, if my drive loses 5% power between the crank and the ground, and your's loses 2%, and both of our crank meters read 250 watts, which of us produced more power?
If he wanted a simple physics answer to torque/cadence/power that's one thing. From the OP post I infer two questions. IS it a basic physics question (no), and what effect does cadence have on power? Do the crank meters read the same - yes, presuming that they're accurate. Include cyclists in the scenario, as he does, well then there's a difference.
If I have expended 800 kilojoules for an hour, and you have expended 1000 for an hour, yet both of our power meters read 250 watts, which of us produced more power?
Secondly, if my drive loses 5% power between the crank and the ground, and your's loses 2%, and both of our crank meters read 250 watts, which of us produced more power?
If he wanted a simple physics answer to torque/cadence/power that's one thing. From the OP post I infer two questions. IS it a basic physics question (no), and what effect does cadence have on power? Do the crank meters read the same - yes, presuming that they're accurate. Include cyclists in the scenario, as he does, well then there's a difference.
1) You are conflating power and energy. They are related but different. Energy measures the work that's delivered. Power measures the rate at which it is delivered.
2) He literally asked a simple physics question and you inferred a more complicated question than the one posed.
Again, I'm not saying you are wrong; just that the question was asked and answered several times in the first 10 posts, yet this thread has gone on for many pages arguing about a question that wasn't asked. It may be a related question; it may be a more interesting question; but it's not the question originally asked.
Which makes this thread a leading contender for 41-iest Thread of the Year.
#144
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I get what the supposed idea is, however I find I tire faster above 85-90 rpm or so, which is consistent with the finding, that just spinning the crank at high rpm is tiring even if no real work is produced.
#145
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Probably a basic physics question. Is wattage affected by cadence? If, say, two identical riders on identical bikes are riding together, same speed; one is in a large gear pedaling at ~70rpm, while the other is spinning at 110+rpm. Is one producing more watts than the other?
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Not trying to be picky, but he literally asked if it WAS a simple physics question. It's only a simple physics answer if you ignore the variables. To put it bluntly, only kbarch got it close to right, and he also neglected that drive train efficiency is also part of the "simple physics" answer (which invalidates ALL of the first 10 answers).
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No, the power at the crank is the same, but one rider may tire faster than the other, even if they are identical, due to the physiologic effects of riding a different cadences. The debate then, is what cadence is the best. The answer to that question is, Imo, it depends ... :-)
A lower cadence and/or a better chainline will have lower drivetrain friction losses
#148
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#149
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I dont buy the "higher rpm is more efficient" dogma. Try Spinning at 120 rpm on a very light load compared to 80 rpm. At 120 you spend a lot of energy just moving yous legs up and down, spinning the crank, even without doing any real work (moving the bike). Just try it out and you'll see.
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"Is one producing more watts than the other?"
You, and others apparently, are assuming that this can only mean power at the crank, propelling the bike forward. That assumption is incorrect, and not just technically. He wanted to know if there is any difference in regards to the power a given rider can provide, given different cadences.
Obviously, if you could provide 250 watts for an hour at 80 rpm, and only 200 watts for an hour at 140 rpm, you would have to agree that you produce more watts at the 80 cadence. The situation is nowhere near that drastic, but where there IS even a small difference, it is precisely what he was asking.
You, and others apparently, are assuming that this can only mean power at the crank, propelling the bike forward. That assumption is incorrect, and not just technically. He wanted to know if there is any difference in regards to the power a given rider can provide, given different cadences.
Obviously, if you could provide 250 watts for an hour at 80 rpm, and only 200 watts for an hour at 140 rpm, you would have to agree that you produce more watts at the 80 cadence. The situation is nowhere near that drastic, but where there IS even a small difference, it is precisely what he was asking.
The other thing closely associated with this is how much energy it takes to produce those watts.
To your example - Junior gears in adult races. I've always argued that the kids having to spin 140 where the adults spin 100 was unfair. People post back it does not really matter, and you just need to learn to spin. I never see a road cyclist spinning 140 when they have the opportunity to shift - they do.